HM Revenue & Customs has been given an extra £71m by the Treasury to take on more staff and improve its customer service levels.
November's government-wide Spending Review saw the tax authority asked to make savings of 18% to its running costs by the end of the parliament, with many of those savings expected to come from job cuts and the consolidation of its 170 offices into 13 regional centres.
But under plans dubbed "Maxing Tax Digital" the Treasury is allowing HMRC to plough £1.3bn back into online services over the next five years, in a bid to change the way tax is administered.
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Wednesday's Budget pledged a further £71m investment in HMRC's frontline operations "to improve the service it provides taxpayers".
According to the Treasury, the money will go towards running a "a 7-day a week service by 2017", with extended hours and Sunday opening for HMRC's online services and tax phone lines.
HMRC will also take on 800 new staff in its call centres, and the Treasury said a new "dedicated phone line and online forum" would be set up to help businesses and the self-employed file tax returns and make the leap to using digital services.
The extra funding comes after Treasury committee chair Andrew Tyrie warned that many small businesses were concerned that there had been a "lack of detailed explanation" of how HMRC's Making Tax Digital plans will play out.
In a letter to ministers published earlier this month, the Conservative MP said that while the Making Tax Digital proposals "may be a sensible direction of travel", they could leave behind " those who do not currently use computers or for whom quarterly reporting would be a substantial burden".
He added: "The government should consult widely before reaching any decisions on this. The requirement for all businesses to maintain a digital tax account needs to be tempered by provisions for those for whom this would be an unreasonable burden. Nor should an ambitious timetable be imposed at the expense of greater clarity for the millions of businesses these changes will affect."